1. Field of the Invention
The present invention relates to a direct image-recording device and an image forming apparatus using same, such as a printer, a facsimile device, and a copier.
2. Description of the Related Art
A direct image-recording device in which an image is directly recorded on a recording paper or a transfer body has been known, this recording process being called toner jetting, direct toning, and toner projection. In such a direct image-recording device, a jetted-out image forming agent is caused to adhere directly to a recording paper and the image is directly formed on the recording paper or transfer body, without developing a latent image formed on a photosensitive body with an image forming agent such as a toner and transferring the developed image from the photosensitive body onto the recording paper or transfer body as in an electrophotographic process.
The conventional direct image-recording device is configured, for example, as disclosed in Japanese Patent No. 2,910,019, by a toner carrying roller that carries a charged toner on the surface thereof, a flexible printed substrate (FPC) serving as a hole forming member that has a plurality of holes formed therein, a plurality of ring-shaped jetting electrodes that are formed on the surface side opposite the toner carrying roller so as to surround the holes, and a counter electrode that faces the toner carrying roller below the flexible printed substrate (FPC). The recording paper is conveyed by a conveying means on the counter electrode.
The toner carrying roller is, for example, in a grounded state and carries on the surface a toner charged to a negative polarity. Where a jetting voltage of a positive polarity is applied to the jetting electrode, an electric field of a predetermined intensity acts upon the toner position opposite the jetting electrode on the toner carrying roller or to the toner in the vicinity thereof. Under the effect of this electric field, the electrostatic force applied to the toner exceeds the adhesion force between the toner and the toner carrying roller, toner aggregates are selectively jetted out from the toner carrying roller in the form of dots and introduced into the holes. The toner is then pulled by an electric field formed between the jetting electrode and the counter electrode that has a higher electric potential than the jetting electrode, and the toner continues flying through the holes, adheres to the surface of the recording paper, and forms a dot image.
In such as a direct image-recording device, the toner supply gap, which is a clearance between the toner carrying roller and the FPC, has to be set and maintained with high accuracy in order to obtain a high-quality image with good dot image density and resolution. For this reason, in such a conventional direct image-recording apparatus, positioning members that abut against the hole forming member where a plurality of holes have been formed and position the hole forming member with respect to the toner carrying roller have been provided at both axial ends of the toner carrying roller. By positioning the toner carrying roller with respect to the hole forming member with these positioning members, it is possible to set the toner gap, which is a clearance between the toner carrying roller and the hole forming member, to a predetermined distance.
However, in the direct image-recording device of such a configuration, the hole forming member comes into contact with the positioning members only in very small zones at both axial ends of the toner carrying roller and the position of the hole forming member is set in the so-called two-end supported state. As a result, deflection or distortion is easily caused by own weight of the hole forming member in the vicinity of the central portion thereof in the axial direction of the toner carrying roller. In particular, where the hole forming member is fabricated from a flexible material such as a flexible printed substrate, the deflection or distortion of the hole forming member in the vicinity of the central portion thereof in the axial direction of the toner carrying roller becomes significant. The resultant problem is that where such a deflection or distortion occurs in the hole forming member, a spread occurs in the toner supply gap in the axial direction of the toner support roller and the predetermined toner supply gap cannot be maintained over the axial direction of the toner carrying roller.